When implementing systems using gigabit serial data transmissions in cables or in backplane transmission lines, you're very limited in the lengths you can achieve because of the severe attenuation and distortion. An established way to compensate is to use equalization at the receiver.
The equalizer anticipates the distortion and adds corrective measures that enable you to implement higher-speed interfaces over longer signal paths. Now, you can buy such equalizers for some standard serial interfaces that run as fast as 10 Gbits/s. For example, National Semiconductor's DS64EV400 programmable quad equalizer compensates for medium losses and reduces deterministic jitter for four data channels.
Part of National's PowerWise product portfolio, the chip consumes 94 mW per channel. With these equalizers, you can boost signal strength as much as 20 dB on up to 10 m of CAT5 cable or up to 40 in. of FR-4 pc-board backplane up to 6.4 Gbits/s and up to 30 in. for FR-4 at rates to 10 Gbits/s. Equalizer output has a low 0.175 UI (unit interval) of residual jitter.
The DS64EV400 is designed for use with FPGAs and ASICs in building systems using any of the high-speed buses like Fibre Channel and Ethernet/XAUI. Each equalizer channel has eight equalization levels that all can be set simultaneously by three control pins or individually programmed through a serial management bus (SMB) link.
The chip permits both ac and dc coupling to the data paths and can accommodate long run-length data patterns like PRBS-31 or balanced codes like 8B/10B. The DS64EV400 also uses differential currentmode logic (CML) I/O and is protected against electrostatic discharge (ESD).
The DS64EV400 is made with a proprietary silicon-germanium (SiGe) biCMOS process and comes in a 7- by 7-mm, 48-pin leadless leadframe package (LLP). Supply voltage may be 2.5 or 3.3 V. The DS32EV400 is available for data rates up to 3.2 Gbits/s. Pricing is $16 for the DS64EV400 and $13 for the DS32EV400 in 1000-unit lots.
National Semiconductor www.national.com
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